| MgO衬底上YBa2Cu3O7-δ台阶边沿型约瑟夫森结的制备及特性 |
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| 引用本文： | 王宏章,李宇龙,徐铁权,朱子青,马平,王越,甘子钊.MgO衬底上YBa2Cu3O7-δ台阶边沿型约瑟夫森结的制备及特性[J].物理学报,2021(3):232-240. |
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| 作者姓名： | 王宏章 李宇龙 徐铁权 朱子青 马平 王越 甘子钊 |
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| 作者单位： | 北京大学物理学院 |
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| 基金项目： | 国家重点研发计划(批准号:2017YFC0601900);国家自然科学基金(批准号:61571019)资助的课题。 |
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| 摘 要： | MgO衬底上的YBa2Cu3O7-δ(YBCO)台阶边沿型约瑟夫森结(台阶结)在高灵敏度高温超导量子干涉器(superconducting quantum interference device,SQUID)等超导器件研制方面具有重要的应用价值和前景.本文对此类YBCO台阶结的制备和特性进行了研究.首先利用离子束刻蚀技术和两步刻蚀法在MgO(100)衬底上制备陡度合适、边沿整齐的台阶,然后利用脉冲激光沉积法在衬底上生长YBCO超导薄膜,进而利用紫外光刻制备出YBCO台阶结.在结样品的电阻-温度转变曲线中,观测到低于超导转变温度时的电阻拖尾现象,与约瑟夫森结的热激活相位滑移理论一致.伏安特性曲线测量表明结的行为符合电阻分路结模型,在超导转变温度TC附近结的约瑟夫森临界电流密度TC随温度T呈现出(TC-T)^2的变化规律,77 K时JC值为1.4×10^5 A/cm^2.利用制备的台阶结,初步制备了YBCO射频高温超导SQUID,器件测试观察到良好的三角波电压调制曲线,温度77 K、频率1 kHz时的磁通噪声为250μΦ0/Hz^1/2.本文结果为进一步利用MgO衬底YBCO台阶结研制高性能的高温超导SQUID等超导器件奠定了基础.
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| 关 键 词： | YBA2CU3O7-Δ 台阶结 超导量子干涉器 |
Fabrication and characterization of YBaCuO step-edge Josephson junctions on MgO substrate for high-temperature superconducting quantum interference devices |
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| Wang Hong-Zhang,Li Yu-Long,Xu Tie-Quan,Zhu Zi-Qing,Ma Ping,Wang Yue,Gan Zi-Zhao.Fabrication and characterization of YBaCuO step-edge Josephson junctions on MgO substrate for high-temperature superconducting quantum interference devices[J].Acta Physica Sinica,2021(3):232-240. |
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| Authors: | Wang Hong-Zhang Li Yu-Long Xu Tie-Quan Zhu Zi-Qing Ma Ping Wang Yue Gan Zi-Zhao |
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| Affiliation: | (State Key Laboratory for Mesoscopic Physics,Applied Superconductivity Center,School of Physics,Peking University,Beijing 100871,China) |
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| Abstract: | The YBa2Cu3O7-δ(YBCO)step-edge Josephson junction on MgO substrate has recently been shown to have important applications in making advanced high-transition temperature(high-TC)superconducting devices such as high-sensitivity superconducting quantum interference device(SQUID),superconducting quantum interference filter,and THz detector.In this paper,we investigate the fabrication and transport properties of YBCO step-edge junction on MgO substrate.By optimizing the two-stage ion beam etching process,steps on MgO(100)substrates are prepared with an edge angleθof about 34°.The YBCO step-edge junctions are then fabricated by growing the YBCO thin films with a pulsed laser deposition technique and subsequent traditional photolithography.The resistive transition of the junction shows typical foot structure which is well described by the Ambegaokar-Halperin theory of thermally-activated phase slippage for overdamped Josephson junctions.The voltage-current curves with temperature dropping down to 77 K exhibit resistively shunted junction behavior,and the Josephson critical current density JC is shown to follow the(TC—T)^2 dependence.At 77 K,the JC of the junction reaches 1.4×10^5 A/cm^2,significantly higher than the range of 10^3-10^4 A/cm^2 as presented by other investigators for YBCO step-edge junctions on MgO substrate with comparable θ of 35°-45°.This indicates a rather strong Josephson coupling of the junction,and by invoking the results of YBCO bicrystal junctions showing similar values of JC,it is tentatively proposed that the presently fabricated junction might be described as an S-s’-S junction with s’denoting the superconducting region of depressed TC in the vicinity of the step edge or as an S-N-S junction with N denoting a very thin non-superconducting layer.By incorporating the MgO-based YBCO step-edge junction,high-TC radio frequency(RF)SQUID is made.The device shows decent voltage-flux curve and magnetic flux sensitivity of 250μΦ0/Hz^1/2 at 1 kHz and 77 K,comparable to the values reported in the literature.To further improve the RF SQUID performance,efforts could be devoted to optimizing the junction parameters such as the junction JC.By using the YBCO step-edge junction on MgO substrate,high-TC direct current SQUID could also be developed,as reported recently by other investigators,to demonstrate the potential of MgO-based step-edge junction in making such a kind of device with superior magnetic flux sensitivity. |
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| Keywords: | YBa2Cu3O7-δ step-edge junction superconducting quantum interference device |
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